In the LTE system, the method for automatically acquiring transmission address information of an opposite eNB and establishing an X2 interface connection is as follows, as shown in FIG. 1.
In step 101, an eNB1 acquires information of a Global eNB ID and a tracking area identity (TAI) of an eNB2, and the eNB1 sends an eNB Configuration Transfer message to a Mobile Management Entity (MME), in which information of the eNB1 is filled into a Source eNB-ID and the information of the eNB2 is filled into a Target eNB-ID, and self-organized network (SON) information is selected as a SON Information Request.
In step 102, after the MME receives this message, it judges that the type of the SON Information is the SON Information Request, then the MME transmits this message transparently to the eNB2 at a target side, wherein the name of the message is an MME Configuration Transfer message.
In step 103, after the eNB2 receives this message, it organizes and sends an eNB Configuration Transfer message to the MME, in this message the SON Information is selected as a SON Information Reply, and an IP address and a port number, which are used to connect with an X2 interface of the eNB1 at a source side, are filled into the SON Information Reply.
In step 104, after the MME receives the message, it judges that the SON Information is the SON Information Reply, then the MME transfers this message transparently to the eNB1 at the source side, wherein the name of the message is the MME configuration transfer message; after the eNB1 at the source side receives this message, it acquires the IP address and the port number of the X2 interface connection of the eNB2 at the target side, and then a coupling can be established on a Stream Control Transmission Protocol (SCTP) layer.
At present, there are two methods about how to acquire the information of an opposite party so as to acquire the IP address:
1. by a background configuration;
2. by an Automatic Neighbour Relation (ANR) function.
The ANR function is described briefly below.
The ANR function is located within the eNB and manages a Neighbour Relation Table (NRT) in concept. The ANR function includes a neighbour cell detection function that is able to discover a new neighbour cell and add it into the NRT. The ANR function also includes a neighbour cell deletion function that is able to delete the expired neighbour relation. Both the neighbour cell detection function and the neighbour cell deletion function belong to the content implemented by the manufacturers.
The Neighbour Cell Relation (NR) defined in the ANR is as follows:
The NR existing between a serving cell and a target cell means that a source cell controlled by the eNB knows an E-UTRAN Cell Global Identifier (ECGI)/a Cell Global Identifier (CGI) and a Physical Cell Identifier (PCI) of the target cell; the source cell has records for the source cell identifying the target cell in the NRT; and the source cell contains attributes defined in the NRT, and the attributes can be set by an Operation, Administration and Maintenance (OAM) function or be directly configured to default attribute values.
For each cell in the eNB, the eNB maintains and manages the corresponding NRT table, and for each NR, the NRT contains the Target Cell ID (TCI). For an E-UTRAN cell, the TCI represents ECGI and PCI of an E-UTRAN target cell.
Automatic neighbour cell generation and optimization is divided into the following two scenarios:
1) Intra-LTE/frequency Automatic Neighbour Relation Function;
2) Inter-RAT/Inter-frequency Automatic Neighbour Relation Function.
The solution for the first scenario is as follows.
The realization of the ANR function is shown in FIG. 2.
In step 201, a serving cell A of an eNB has an ANR function and acts as a part of a normal call flow, and the eNB notifies each user equipment (UE) to measure neighbour cells; wherein the eNB can use different strategies to notify the UE to perform measurement and when to report a measurement result.
In step 202, the UE sends the measurement result related to a cell B, where this result includes a PCI instead of an ECGI of the cell B; when the eNB receives a measurement report containing the PCI sent by the UE, proceed to the next step.
In step 203, the eNB notifies the UE to read the ECGI, a Tracking Area Code (TAC) and all available Public Land Mobile Network (PLMN) IDs of the relevant neighbour cell using the newly discovered physical cell ID (namely, the ID of the cell B) as a parameter; therefore, the eNB needs to schedule an appropriate idle cycle to allow the UE to read the ECGI of the measured neighbour cell.
In step 204, the UE acquires the ECGI of the cell B by reading a Broadcast Channel (BCH).
In step 205, the UE reports the acquired ECGI of the cell B to the eNB of the cell A.
The eNB decides to add this neighbour cell relation in and can use the PCI and the ECGI to:
a, find a transport layer address of a new eNB;
b, update its NR list;
c, if necessary, establish an X2 interface connection with the new eNB.
For the second scenario:
Since the X2 interface is only defined in the E-UTRAN, the Inter-RAT situation is not concerned but only the inter-frequency situation is concerned here. The whole flow is similar to that in the first scenario and is not described in detail here.
If necessary in the inter-frequency scenario, the eNB can use the information detected by the UE to establish a new X2 interface connection.
In summary, the two methods in the related art have the following problems:
the method using the background configuration hands tedious work of configuring the neighbour eNB information to the operator; and
the method for acquiring via the ANR makes the UE interact with the eNB very frequently for the neighbour cell detection, which increases air interface overhead.